Suthakorn’s fourth and final project presented here
was to design and build a fully autonomous self-replicating robotic system [1287,
1289]. This work took place under the direction
of professor Gregory Chirikjian; also, Andrew Cushing, a local high school student,
assisted in the building of the device. The robot and its replicas each consist
of four separate complex parts or “subsystems”: controller, left
tread, right tread, and gripper/sensor components (Figure
3.76(A), caption).
The prototype device used two light sensors to detect objects and track lines
(blue-painted lines and silver spots) for navigation on the 2 meter x 3 meter
work surface. Magnets and shape-constraining blocks helped to align and interlock
the complex parts during replication (Figure
3.76(B), caption).

The replica’s parts are prepositioned at known locations
and the original robot starts at the initial position (Figure
3.76(C), caption).
The explicit replication procedure is worth quoting verbatim from Suthakorn
[1287] in its entirety:

The original robot starts following the line from the starting point
to the first subsystem (the “right tread” complex part) using
sensor No. 1.

Once light sensor No. 2 detects the first subsystem (right tread), the
original robot stops and begins the grasping process, then grasps the right
tread subsystem.

After the grippers are closed, the original robot will turn to the right
until it detects a line.

The original robot will follow the second line until it reaches the assembling
spot.

When light sensor No. 1 on the original robot detects the silver acrylic
spot (the assembling spot), the robot will stop and begin the attaching
process.

The original robot opens the grippers and gives a final push to secure
the right tread subsystem (of the replica) to the controller subsystem (of
the replica).

The original robot then backs up and turns to the left until it detects
a line value on sensor No. 1.

The original robot follows the line until it reaches the left tread subsystem.

Once light sensor No. 2 detects the second subsystem, the robot will
stop, and begin the grasping process by closing its gripper around the left
tread’s wedge.

The original robot turns right until it detects the next line.

The original robot will follow the second line until it reaches the assembling
spot.

Once the original robot reaches the assembling spot, it begins the attaching
process.

The original robot opens its gripper to release the left tread subsystem.

The original robot gives a final push on the left tread subsystem to
help secure it.

The original robot then backs up and turns left until it detects the
next line, using sensor No. 1.

The original robot follows the line to the final subsystem.

Once it reaches the gripper/sensor subsystem, it will stop and begin
the grasping process.

The original robot closes its gripper and turns right until it detects
a line value with sensor No. 1 (Figure
3.76(D), caption).

The gripper/sensor subsystem is now transferred to the assembling spot.

Once the original robot reaches the assembling spot it will stop and
open the gripper.

The original robot backs up and turns left until sensor No. 1 is a line
value.

The original robot then follows the line back to the starting point and
is ready to replicate the next replica system.

The finished replica robot self-activates 20 seconds after completion
and begins following the line to the starting point.

Once each robot reaches the starting point, it begins the replication
procedure again.

Following this cookbook-like procedure, the original robot
was capable of automatically assembling its replicas. The replication process
took 135 seconds per cycle. While each of the four complex parts had to be placed
in known locations, “the errors of positioning and orientation are not
highly critical. We found slight errors during the grasping process in a few
experiments (out of more than 20 trials) caused by improper placement of the
subsystems. Overall, the system is robust and repeatable.” An AVI video
clip is available online [1293].

In future work, Suthakorn planned “to build a self-replicating
intelligence system [1290] such as a circuit
controller and a mechanical decoder. This would fill the missing part of the
self-replicating robotics research. However, our ultimate goal is to develop
a self-replicating robotic system capable of autonomously assembling its replicas
from simple components using only electromechanical intelligence, i.e., a mechanical
code and transistor-based control circuits. This eliminates complicated electronic
components such as programmable micro-controllers, and makes the concept more
appropriate for future space systems that can use in-situ resources for self-replication.”
[1287] Pursuing this objective, the syllabus
for the Spring 2003 mechatronics course [30] at
the JHU Department of Mechanical Engineering, called “the intelligence
of self-replicating robots,” is described as follows:

This course is a hands-on, interdisciplinary design
project, in which juniors, seniors, and graduate students from all engineering
disciplines work together to design, build, and debug robots. This year we
continue the exploration of self-replicating robots. Last year, each group
built a remote-controlled self-replicating robot. This year our goal is to
build autonomous self-replicating electromechanical intelligences. Each group
will build a robot consisting of an arm, a control circuit for the arm, and
a machine code program to control the arm, among which the circuit and the
code should be replicable. The objective is that the arm should be able to
implement the same function as before, after being connected to the resulting
new circuit and code. The whole system will be built by using LEGO kits. Students
are required to build their own logic control circuits which are made up of
LEGO pieces embedded with electronic components, such as transistors, resistors,
and capacitors. The “program” will also be built with LEGO pieces,
and should consist of at least 10 bits but not more than 100 bits. Presentation
will be within the week from May 5 to 9, 2003.

Interestingly, Suthakorn’s autonomous replicator passed
the “fertility test” recommended by the RSC Team of the 1980 NASA
lunar replicator study [2] for their replication
feasibility demonstration (Section 3.13.1): “All
the replicas were also capable of completing the same replicating process,”
says Suthakorn [1287]. “We believe
that this prototype was the world’s first fully functional autonomous
self-replicating robot.”